The proposed research addresses the broad SRP theme of Detection Research and more specifically the development of passive samplers for multi-chemical detection and determination of the degree of bioavailability in water and sediment. Aim 1 will develop a universal passive sampling device (PSD) for measuring the time-weighted-average chronic exposure to hundreds of organic chemicals in water. We will advance the theory, design, and application of PSDs to a very broad range of physico-chemical properties (e.g., KOW = 0-9) so that nearly every organic chemical on the Superfund Priority List of Chemicals, and many of their metabolites, will be sampled by a single PSD. We hypothesize that a mixed-polymer sorptive phase contained within a non-selective and highly porous membrane will allow linear uptake of nearly all organic chemicals. Aim 2 will establish the use of PSDs to measure the bioavailable fraction of PCBs and PCB metabolites in water, sediment, and soil. We will conduct laboratory bioavailability experiments with PCB-contaminated soil, sediment and water to advance our understanding of the mechanisms controlling PCB bioavailability and perform field verification at NPL sites. In collaboration with Project 1, we will use extracts of our samples to determine the relationship of our bioavailability measure to the dioxin toxic equivalency factor response in Project 1 cell assays. Aim 3 will establish the use of PSDs to measure the bioavailable fraction of PAHs and PAH metabolites in water, sediment, and soil. In collaboration with Project 5, we will perform studies very similar to those in Aim 2 to develop the use of PSDs to measure PAH and PAH metabolite bioavailability under both controlled laboratory conditions and at NPL sites. This work will advance our understanding of and ability to measure the partitioning of PAHs and metabolites among dissolved organic carbon, soft and hard (soot) particulate carbon, weathered oil/oil product phases, and biota. We hypothesize that our novel PSD design will provide an accurate measure of bioavailable chronic exposure under a broad range of conditions and that PSD-derived data will overcome a critical barrier to more accurate estimates of bioavailability and risk.